The pathogen Bordetella pertussis elaborates a number of virulence factors during the course of disease. The production of many of these factors is coordinately regulated through the two component regulatory locus bvg, in response to environmental stimuli. Our previous work has identified a number of previously uncharacterized proteins which are regulated by this locus and are produced together with the more thoroughly studied virulence determinants filamentous hemagglutin and pertussis toxin. We have termed two of these determinants Tcf and Bpf. B. pertussis mutants which no longer produced these proteins were defective in their ability to colonize mice in an aerosol challenge model. The expression of Tcf and Bpf appears to be unique to strains of B. pertussis, the other species of Bordetella do not have the gene encoding Tcf although they do appear to have DNA homologous to that encoding Bpf. The genes encoding these proteins have been cloned and sequenced. The C-terminal 30kDa fragments of Tcf and Bpf are very similar to the C terminus of another B. pertussis protein, pertactin. All belong to an emerging family of secreted proteins which are made as large precursors. The C-termini may function to export these proteins across the bacterial cell envelope. After export cleavage may occur with the mature protein remaining attached to the cell surface, as is pertactin, or released into the supernatant as is Tcf. Bpf does not possess a protease recognition site and cleavage does not appear to occur. This type of export system may exist in other bacteria, in the Enterobacteriaceae the E.coli adhesin AIDA-1 is made as a large precursor as is the Shigella flexneri protein IcsA. In both cases the mature protein is 30kDa smaller than the precursor. Our future studies will concentrate on the contribution of the C termini of Tcf and Bpf to secretion of these proteins by B. pertussis and the contribution of these proteins to B. pertussis pathogenesis.